Super acceleration from continental to oceanic rifting

Continental rifting and oceanic spreading are end-members of lithospheric extension, yet the transition between them is not a smooth kinematic continuum. Using a representative global dataset of continental rifts, transitional breakup systems and oceanic ridges, I compare extension or spreading rate, surface heat flow, lithospheric thickness and characteristic duration. Continental rifts typically operate at ~ 0.1–10 mm/yr and may persist for tens to more than one hundred million years, whereas oceanic spreading commonly occurs at ~ 10–150 mm/yr under a higher-heat-flow, thinner-lithosphere regime. Transitional systems such as Afar and the Red Sea occupy an intermediate field but already display strong thermal weakening and faster rates. Across the combined dataset, heat flow increases and lithospheric thickness decreases with log-rate moving from continental to oceanic rifting. Regression analysis reveals a non-linear acceleration of extension rates, with an increase of up to one or two orders of magnitude from continental to oceanic domains. This transition reflects a shift from strength-controlled lithospheric rift-resisting to other processes, such as a more effective shearing from below or from above active on the escaping plate. This confirms the asymmetry of rifts and questions the mechanism determining plate tectonics since plates can spread apart without any lateral slab pull. For example, North and South America plates move westerly relative to the mantle, without any attached slab which could drag them, indicating that slab pull is neither necessary nor sufficient to drive the process. I propose that rift acceleration is controlled by progressive lithosphere–asthenosphere decoupling. As the lithosphere thins and ruptures, a continuous lower-viscosity layer in the Low Velocity Zone (LVZ) beneath the western plate with respect to the LVZ of the conjugate plate could explain the faster westerly motion of the plate and the faster spreading rate once the continental lithosphere is spread apart. This model aligns with the westward net rotation of the lithosphere, which is triggered by the low-frequency horizontal component of the body tide. Here, velocity gradients among tectonic plates are controlled by viscosity gradients in the low-velocity zone. Continental rifting may persist for > 100 Myr at low extension rates. Extension accelerates non-linearly toward oceanic breakup. Heat flow increases and lithosphere thins moving from continental to oceanic rift. Oceanization implies 5 to 100 times faster spreading. Faster western plate due to a lower-viscosity LVZ. Acceleration reflects lithosphere–asthenosphere decoupling.